Nausea, vomiting, stomach upset, gas, shaking (tremor), constipation, dry mouth, lightheadedness, dizziness, or drowsiness may occur. If any of these effects persist or worsen, notify your doctor or pharmacist promptly. To lower your risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position. To prevent constipation, maintain a diet adequate in fiber, drink plenty of water, and exercise. If you become constipated while using this drug, consult your pharmacist for help in selecting a laxative (e.g., stimulant-type with stool softener). Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. Tell your doctor immediately if any of these unlikely but serious side effects occur: mental/mood changes, fainting, seizure, fast/irregular heartbeat, increased thirst/urination, slow/shallow breathing, hearing changes (e.g., ringing in the ears), easy bruising/bleeding, signs of infection (e.g., fever, persistent sore throat), heartburn, discomfort when swallowing, dark urine, yellowing eyes/skin, change in the amount of urine, unusual tiredness. Seek immediate medical attention if any of these rare but very serious side effects occur: black stools, severe stomach/abdominal pain, vomit that looks like coffee grounds, slurred speech, weakness on one side of the body. A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist. In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.